Research will be pursued in three areas: effects of hallucinogens on aggression, behavioral tolerance to marihuana and effects of marihuana on goal directed behavior. Aggression studies will concentrate on the mechanism by which mescaline produces violent aggressive behavior in rats. Tolerance studies will concentrate on the interaction between environmental events and drug administration in the development of tolerance. Preliminary data indicate that exposure of subjects to arousal producing situations following drug administration leads to accelerated tolerance development. Additional confirmation of this finding will be sought. Studies of marihuana and goal directed behavior will explore the effects of delta-9-THC on intracranial self-stimulation. Recently completed studies suggest that impairment of self-stimulation by THC is a result of depletion of catecholamines. Tests of this hypothesis will be carried out in a series of studies involving interactions between THC and other drugs in the self-stimulation situation and in studies of cross tolerance between THC and other drugs, particularly reserpine and its congeners.